This invention relates to a two-flow-passage type exhaust gas driven turbo-charger, and, more particularly, to a two-flow-passage type exhaust gas driven turbo-charger suitable for preventing the thermal fatigue destruction of a partition.
A two-flow-passage type exhaust gas driven turbo-charger is used for the purpose of improving the super-charging capability with respect to the low-speed rotation of an engine by utilizing exhaust pulses or narrowing of the flow passages so as to increase the flow rate of a gas. In a turbo-charger of such a construction, a scroll casing is divided radially by a partition including an annular plate, in such a manner that the flow passages are independent of each other in an interior defined by an inner surface of the scroll casing. A radial flow type turbine wheel is provided in the casing, and the supercharging of the engine is affected by a compressor connected to the turbine wheel. A flow passage valve is provided which is closed when the engine has a low rotational speed, to increase the flow rate of the gas due to the narrow passages. While the turbo-charger of this construction is in operation, the temperature of the partition becomes higher than those of other portions thereof due to the high-temperature gas, so that the turbo-charger is compression-plastically deformed. When this turbo-charger is not in operation, the temperatures of all parts thereof become uniform, so that a tensile stress occurs therein. When the turbo-charger is repeatedly operated and stopped, especially, when the starting of the turbo-charger is suddenly started with the exhaust gas having a high temperature, a crack occurs in some cases in the partition due to the thermal fatigue. This thermal strain occurs due to a difference between the temperature of the partition and that of the outer surface of the casing to which the partition is fixed. However, the failure problems due to thermal fatigue failure of the partition have not been realized. The techniques relating to a turbo-charger of aforementioned type is disclosed in, for example, U.S. Pat. No. 3,614,259.
An object of the present invention is to provide a turbo-charger which is capable of preventing the thermal fatigue failure of a partition by minimizing a difference between the temperature of the partition and that of the outer surface of the portion of a casing to which the partition is fixed.
To achieve the above object, the invention provides a two-passage type exhaust gas driven turbo-charger in which the outer surface of the portion of a casing to which a partition is fixed is covered with a heat-insulating material to promote an increase in the temperature of this portion of the casing and thereby minimize temperature differential between the casing and the partition so as to prevent thermal fatigue failure of the partition caused by the thermal strain occurring therein.
In accordance with further features of the present invention a two-passage type exhaust gas driven turbo-charger is provided in which a free end portion of a partition is covered with a heat-insulating material to suppress an increase in the temperature of the free end portion of the partition and thereby minimize the difference between the temperature of the casing and that of the partition so as to prevent the thermal fatigue failure of the partition caused by the thermal strain occurring therein.
In accordance with still further advantageous features of the present invention a two-passage type exhaust gas driven turbo-charger is provided in which a through bore is provided in the portion of a casing to which a partition is fixed to introduce a high-temperature exhaust gas thereinto and thereby minimize the temperature differential between the temperature of the casing and that of the partition, so as to prevent the thermal fatigue failure of the partition caused by the thermal strain occurring therein.
According to the present invention a two-passage type exhaust gas driven turbo-charger is provided in which a thickness of a root portion of a partition is smaller than that of a free end portion thereof to thereby minimize the temperature differential between the temperature of a casing and that of the partition so that the thermal fatigue failure of partition caused by the thermal strain occurring therein can be prevented.